This multidisciplinary program emphasizes selected events that influence fertility and the reproductive processes before fertilization in primates. The events under investigation include (1) the chemical steps leading to the induction of motility in immature, immotile sperm and the reversibility of this sequence, (2) the purification of a forward motility protein in the male reproductive tract, its distribution in body fluids and tissues, and the hormonal requirements for its synthesis, (3) the role of estradiol-17 beta and progesterone in epithelial and endometrial differentiation in the oviducts and uterus, (4) the role of steroid receptor proteins in the oviducts and uterus, (5) evidence for an oviductal forward motility protein, (6) the role of estrogens, progestins, and androgens in the regulation of gonadotropins, (7) the function of steroid-converting enzyme activities in the uterus, pituitary gland, and hypothalamus, (8) the neuroendocrine control of gonadotropin-releasing secretion and action on pituitary gonadotropes, (9) the effect of monoamines, particularly dopamine and serotonin, on gonadotropin-releasing hormone secretion, (10) the interaction of prolactin and the gonadotropins in the neuroendocrine events that modulate the secretion of these pituitary hormones, (11) the physiological significance of a nonsteroidal secretory product from the ovaries and testes that inhibits the release of follicle-stimulating hormone, (12) changes in gonadotropin-releasing hormone receptors on surface membranes of pituitary gonadotropes during the estrous and menstrual cycles and the peptide and gonadal hormones that influence the numbers of these receptors.